Filter device and filter element

ABSTRACT

The invention relates to a filter device having a cup-shaped filter housing ( 1 ), comprising a filter element ( 13 ) held therein and having at least one end cap ( 21 ), and a retaining device serving for the detachable fixing of the filter element ( 13 ) along the longitudinal axis ( 3 ) thereof, said retaining device comprising screwing elements ( 33, 41 ) interacting with each other and configured on the interior of the filter housing ( 1 ) and on the filter element ( 13 ), and having a sealing device ( 38 ) forming the seal between the filter element ( 13 ) and a housing terminating part ( 5 ) limiting the filter housing ( 1 ) at an end, characterized in that the housing terminating part ( 5 ) forms an element receiving device having a fluid passage ( 43 ) that is concentric to the longitudinal axis ( 3 ), said fluid passage comprising inner screwing elements ( 41 ), a connecting piece ( 31 ) of the end cap ( 21 ) able to be screwed into said passage using outer screwing elements ( 33 ), and that the sealing device has a sealing element ( 38 ) that is combined with the end cap ( 21 ) to form a cohesive component and that is accommodated in a seat ( 37 ) configured at the transition between the end cap ( 21 ) and the adjacent beginning of the thread turns ( 39 ) of the screwing elements ( 33 ) positioned at the connecting piece ( 31 ).

The invention relates to a filter device having a cup-shaped filter housing, with a filter element which can be accommodated therein and with at least one end cap, and a retaining device which is used for detachable fixing of the filter element along its longitudinal axis and which has screwing elements which interact with one another and which are configured on the inside of the filter housing and on the filter element, and with a sealing device which forms the seal between the filter element and a housing terminating part which borders the filter housing on the end side. The invention furthermore relates to a filter element which is intended for the filter device.

Filter devices for holding of filter elements are readily available on the market in a plurality of versions. A significant portion of production costs in such filter devices is spent on the construction of the retaining device for detachable fixing of the filter element within the pertinent housing and to the sealing device for sealing the interior of the filter element relative to the filter housing.

In a filter device of the aforementioned type which is shown in document WO 2005/123216 A1, in an effort to keep production costs especially low, the sealing device is designed as a one-piece component of a pertinent end cap of the filter element; i.e., it is produced from the same material as the end cap. This construction makes production cheaper and easier, and hence conventional separate sealing devices which extend between a filter element and a housing terminating part can be omitted. In addition, mounting processes are simplified because there is no need to focus on handling separate sealing devices. On the other hand, limitations arise with respect to the quality of the seal which has been formed because plastic materials which are conventional and suitable for production of the end caps cannot all be regarded as suitable sealing materials. This results in limitations in the choice of materials in the production of the end caps. In addition, for a sealing device molded in one piece on the end cap, a close tolerance is necessary in the production of the end caps to ensure a reliable seal.

Proceeding from the prior art, the object of the invention, while retaining the advantages, specifically the simple handling in installation and low production costs, is to provide a filter device which is characterized by an especially reliable seal between the filter element and the filter housing. Furthermore, the object of the invention is to provide a filter element which is suitable for this filter device. These objects are achieved by a filter device with the features of claim 1 in its entirety and a filter element with the features of claim 8.

According to the characterizing part of claim 1, an important particularity of the invention consists in that the housing terminating part, on which the seal can be formed relative to the filter element, is designed as a receiving device of the filter element with a fluid passage which is provided with inner screwing elements and which is concentric to the longitudinal axis of the filter element, and a connecting piece of the end cap can be screwed into the fluid passage of the housing terminating part with external screwing elements, and the sealing device having a sealing element which is accommodated at the same time on the end cap in a seat such that it is combined with the end cap to form a cohesive component. Here, the arrangement is such that the seat of the sealing element is located at the transition between the end cap and the adjacent start of the thread turns of the screwing elements located on the connecting piece of the end cap.

In this positioning of the sealing element, the tightening of the screw union, i.e., the screwing of the connecting piece of the end cap into the fluid passage of the housing terminating part, leads to adhesion between the end cap, the sealing element adjoining it, and the pertinent end of the fluid passage in the housing terminating part, so that the retaining force of the screwing elements at the same time produces the sealing force acting on the sealing element. In that the sealing element with the end cap forms a cohesive component, the mounting process at the same time is made simple and reliable. Moreover, there are no limitations at all with respect to the material choice because the end cap can be molded from suitable plastics regardless of whether a pertinent material is suitable as a sealing material or not. There are likewise no limitations at all with respect to the choice of the material of the sealing element. Rather, a suitable material, for example, an elastomer, especially rubber material, can be chosen at will with respect to the respective requirements, for example, in the form of an O-ring.

Advantageously, the arrangement can be such that the housing terminating part as the bottom part of the filter housing forms the element receiving device for the end cap of the filter element, which cap is assigned to the housing bottom. In a filter element through which flow takes place in the conventional manner from its outer side to an inner filter cavity, by way of the connecting piece of the end cap, the cleaned fluid can drain via the fluid passage of the housing bottom down with a flow direction which runs along the longitudinal axis with little flow resistance.

In especially advantageous exemplary embodiments, the fluid passage of the bottom part is bordered by an annular edge which projects into the interior of the housing and which forms a contact surface for the end cap which adjoins due to the retaining force of the screwing elements. When the screw union is tightened, this results in a defined sealing force which presses the sealing element and which is limited by the positive contact of the end cap with the annular edge of the fluid passage.

In an especially advantageous manner, the arrangement can be such that the fluid passage of the bottom part on the end section bordering the annular edge has an oblique surface which increases the inside diameter toward the annular edge and which forms a sealing surface for the interaction with the sealing element which is fixed on the connecting piece of the end cap. In this way, an especially reliable seal is ensured since the sealing element is pressed both axially and radially by the retaining force of the screwing elements.

In advantageous exemplary embodiments, the sealing element can be a gasket, preferably an O-ring, which is held on the connecting piece in a seat between the flat lower end surface of the end cap which runs in a radial plane, and the first thread turn of the screwing elements of the connecting piece.

The thread turns on the connecting piece of the end cap can be formed as a round thread; this promotes efficient manufacture of the end cap by molding.

In especially advantageous exemplary embodiments, the arrangement can be such that the bottom part has radial ribs which border the flat contact surface with the annular edge, whose axial height decreases toward the peripheral zone of the bottom part. This yields high structural strength of the bottom part with low material cost. At the same time, a narrow toleration of the dimension of the ribs is not necessary because only the contact surfaces with the annular edge interact with the end cap because the ribs run sloped.

The invention is detailed below using one exemplary embodiment which is shown in the drawings.

FIG. 1 shows a perspective, broken away, cutaway and highly schematically simplified representation of only the lower, bottom side end section of a filter device according to one exemplary embodiment of the invention;

FIG. 2 shows a longitudinal section of the lower section of the exemplary embodiment which is shown in FIG. 1;

FIG. 3 shows a partial extract of the region designated as III in FIG. 2, drawn enlarged compared to FIG. 2, and

FIGS. 4 and 5 show a longitudinal section or a side view of only the filter element end cap of the exemplary embodiment.

From a filter housing 1 in the form of a cup which is rotationally symmetrical to the longitudinal axis 3 in its outline, FIGS. 1 and 2 show only the lower, bottom side end section at which the housing 1 is closed off by a bottom part 5. The bottom part 5 can be formed by a metallic injection molded part or a component molded from plastic. On its outer periphery, the bottom part 5 on a flange region 7 is connected to the housing wall which extends upward, on the flange region 7 a seal arrangement 9 being inserted in a peripheral annular groove of the bottom part 5. The filter housing 1 is closed off on the upper part, which is not shown in the drawings, by a housing cover which can of conventional design and has a fluid supply (not shown) via which fluid to be cleaned can be supplied to an outer fluid space 11 which is located on the outer side of a filter element 13 in the form of a filter cartridge. In operation, the fluid to be cleaned flows from the outer space 11 through the filter material 15 of the filter element 13 into an inner filter cavity 17 which forms the clean side in the filtration process and which is located in the interior of a fluid-permeable support pipe 19 which is surrounded by the filter material 15. On the lower end facing the bottom part 5, the support pipe 19 is connected to an end cap 21 of the filter element 13 which also forms an enclosure for the facing end edge of the filter material 15. The end cap 21 can be molded out of plastic in one piece with the support pipe 19 or, as shown in FIGS. 2 and 3, can form a separate component which is joined to the end cap 21.

As is apparent from FIGS. 2 and 3, the bottom part 5 forms the housing terminating part which, for fixing the filter element 13 within the filter housing 1, forms an element receiving device which interacts with the pertinent end cap 21 and on which the sealing takes place at the same time between the filter element 13 and the filter housing 1. The configuration of the end cap 21 of the filter element 13 is shown best in FIGS. 3 to 5, of which FIGS. 4 and 5 show the end cap 21 individually. It is a body of revolution with a central hollow body 23 which is concentric to the axis 3. In the region of its one end 25, the body 23 is surrounded by a radially extending annular body 27 which borders an annulus 29 which is open toward the side of the end 25 and which forms the enclosure for the end of the filter material 15 of the filter element 13, which end is held in the annulus. Proceeding from the annular body 27, the body 23 forms a connecting piece 31 which extends in the axial direction and on whose outer side there are screwing elements 33 in the form of an external thread which is formed as a round thread. Following the flat lower end surface 35 of the annular body 27 facing away from the end 25, on the outer periphery of the connecting piece 31 there is an annular groove-like seat 37 in which a sealing element in the form of a gasket 38 is held and secured between the end surface 35 and the first thread turn 39 such that the gasket 38 with the end cap 21 forms a cohesive component. In other words, the end cap 21 and thus the filter element 13 which belongs to it can contain the sealing element which is necessary for sealing as a premounted component before the pertinent filter element is put into operation.

As is best shown in FIGS. 4 and 5, the gasket 38 in the unloaded state forms a radial projection above the screwing elements 33. Based on this configuration, this results in the seal engagement shown in FIGS. 2 and 3, especially in FIG. 3, with an assigned sealing surface on the bottom part 5, when a retaining force takes effect which secures the filter element 13 in the element receiving device formed by the bottom part 5 and which becomes active by screwing the screwing elements 33 on the connecting piece 31 with assigned screwing elements 41 on the bottom part 5. These screwing elements 41 on the bottom part 5 are formed in an inner concentric fluid passage 43 of the bottom part 5 by sloped ribs which project radially to the inside, of which only one is shown in FIG. 1, and which act as parts of individual sections of thread turns, specifically as parts of a round thread screw union in interaction with the thread turns 39 which are formed as a round thread on the connecting piece 31 of the end cap 21. As FIGS. 2 and 3 show, the fluid passage 43 of the bottom part 5 on the outer lower end is extended by a pipe socket 45 on which the port connection (not shown) for draining the cleaned fluid is formed. On the inner end facing away from the lower pipe socket 45, the fluid passage 43 forms an axially projecting annular edge 47 whose end forms a flat annular surface which runs in a radial plane and which is used as a contact surface 49 for the flat lower end surface 35 of a filter element 13 which is accommodated in the element receiving device which has been formed. In the end section of the opening edge of the fluid passage 43 which extends toward the contact surface 49, it forms a sloped surface 51 which increases the diameter of the fluid passage 43 toward the contact surface 49. The sloped surface, in interaction with the gasket 38, forms the bottom-side sealing surface of the seal between the end cap 21 and the bottom part 5.

As FIG. 3 shows best, with the screw union tightened in which the end surface 35 of the end cap 21 adjoins the contact surface 49, the gasket 38 is pressed between the seat 37 and the sloped surface 51 by the retaining force of the screw union both in the radial direction and also in the axial direction. When the filter element 13 is positioned and fixed on the element receiving device formed by the bottom part 5, sealing thus takes place between the spaces 11 (dirty side in the filtration process) and 17 (clean side), the positive contact of the end surface 35 of the filter element 13 with the contact surface 49 of the annular edge 47 of the bottom part 5 forming a stop device which limits the retaining force when the screw union is tightened, regardless of the tightening moment of the screw union, to a value for which the gasket 38 is pressed on the sloped surface 51 and in the seat 37 such that the sealing force has the strength which is optimum for the material of the gasket 38.

The bottom part 5 does not form a solid body in the upper or inner longitudinal section between the annular edge 47 and the peripheral region 53, but has a sequence of radially extending ribs 55 which are arranged in a star shape. With little material consumption, a high structure strength of the bottom part 5, in particular good compressive strength, is thus achieved. The top 57 of the ribs 55 runs descending from the annular edge 47 toward the peripheral region 53; this increases the distance to the end surface 35 of the adjoining end cap 21 radially to the outside. In this way, without close tolerances having to be adhered to in the molding of the bottom part 5 with respect to the ribs 55, it is ensured that the fixing in position of the end cap 21 takes place only on the contact surface 49 of the annular edge 47.

It goes without saying that instead of the illustrated screwing elements 33, 41 which form a round thread, there could be other screwing elements, for example, a conventional metric thread. Instead of the illustrated combination between the bottom part 5 and the wall of the filter housing 1 which extends upward, by forming a flange region 7 the bottom part 5 could be a screwed housing cover or could be configured in one piece with the adjoining housing wall. 

1. A filter device having a cup-shaped filter housing (1), with a filter element (13) which can be accommodated therein and with at least one end cap (21), and a retaining device which is used for detachable fixing of the filter element (13) along its longitudinal axis (3) and which has screwing elements (33, 41) which interact with one another and which are configured on the inside of the filter housing (1) and the filter element (13), and with a sealing device (38) which forms the seal between the filter element (13) and a housing terminating part (5) which borders the filter housing (1) on the end side, characterized in that the housing terminating part (5) forms an element receiving device with a fluid passage (43) which is concentric to the longitudinal axis (3), said fluid passage having inner screwing elements (41), and into which a connecting piece (31) of the end cap (21) can be screwed with external screwing elements (33), and that the sealing device has a sealing element (38) which is combined with the end cap (21) to form a cohesive component and which is accommodated in a seat (37) configured at the transition between the end cap (21) and the adjacent start of the thread turns (39) of the screwing elements (33) located on the connecting piece (31).
 2. The filter device according to claim 1, characterized in that the housing terminating part as the bottom part (5) of the filter housing (1) forms the element receiving device for the end cap (21) of the filter element (13), which cap is assigned to the housing bottom.
 3. The filter device according to claim 1, characterized in that the fluid passage (43) of the bottom part (5) is bordered by an annular edge (47) which projects into the interior of the housing (1) and which forms a contact surface (49) for the end cap (21) which adjoins due to the retaining force of the screwing elements (33, 41).
 4. The filter device according to claim 3, characterized in that the fluid passage (43) of the bottom part (5) on the end section bordering the annular edge (47) has an oblique surface (51) which increases the inside diameter toward the annular edge (47) and which forms a sealing surface for the interaction with the sealing element (38) which is fixed on the connecting piece (31) of the end cap (21).
 5. The filter device according to claim 4, characterized in that the sealing element is a gasket (38), preferably an O-ring, which is held on the connecting piece (31) in a seat (37) between the flat lower end surface (35) of the end cap (21) which runs in a radial plane, and the first thread turn (39) of the screwing elements (33) of the connecting piece (31).
 6. The filter device according to claim 5, characterized in that the thread turns (39) on the connecting piece (31) are formed as a round thread.
 7. The filter device according to claim 3, characterized in that the bottom part (5) has radial ribs (55) which border the flat contact surface (49) with the annular edge (47), whose axial height decreases toward the peripheral zone (53) of the bottom part (5).
 8. A filter element, especially for use in a filter device according to claim 1, an end cap (21) being joined to at least one end of the filter element (13) and on its side facing away from the filter element (13) having a sealing device (38) which forms the seal between the filter element (13) and a housing terminating part (5) which borders the filter housing (1) on the end side, a retaining device being provided for detachable fixing of the filter element (13) along its longitudinal axis (3) and having screwing elements (33, 41) which interact with one another and which are configured on the inside of the filter housing (1) and on the filter element (13), and the sealing device having a sealing element (38) which is combined with the end cap (21) into a cohesive component and is accommodated in a seat (37) configured on the end cap (21) at the transition to the screwing elements (33) which are molded onto it. 